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Photosynthesis is the process in which light energy, trapped by chlorophyll, is used to convert carbon dioxide and water into glucose and oxygen.

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Introduction

Plan Introduction All living organisms need food. Animals take in 'ready-made' food which they digest. They use the digested products for energy and to build new cells and tissues. Plants also require raw materials for building tissues and a source of energy. They manufacture everything they need out of simple ions and compounds available in the environment. The building up of complex molecules from simpler substances requires energy and enzymes. The enzymes are in the plants cells and the energy comes from sunlight. The process is called photosynthesis. Plants are able to absorb and use light energy because they have a green pigment, chlorophyll, contained in chloroplasts in some of their cells. Chlorophyll allows the energy in sunlight to drive chemical reactions. Chloroplasts act as energy transducers, converting light energy into chemical energy. Photosynthesis is the process in which light energy, trapped by chlorophyll, is used to convert carbon dioxide and water into glucose and oxygen. Carbon Dioxide + Water Glucose + Oxygen 6CO2 + H2O C6H12O6 + 6O2 There are four main things which affect the rate of photosynthesis: * Light intensity * Carbon dioxide * Water * Temperature for enzyme activity These are called limiting factors. Whichever one of these is furthest away from its optimum level most affects the rate of the overall process. ...read more.

Middle

Therefore the closer the light bulb is to the pondweed; the more bubbles should be produced from the stem. I think this because as the light bulb moves towards the pondweed, the light intensity increases, and therefore so should the rate of photosynthesis. This is why plants photosynthesize during the day and not during the night. Before planning this investigation, we completed a trial experiment. The purpose of this was to give us an idea of the experiment we were going to do. This meant that we could avoid making mistakes mid-investigation, and also finding results which do not accurately represent what should occur. Obtaining Evidence To make the experiment as accurate possible I made sure all measurements were the same and made sure that the constants did not vary. If for any reason something didn't go to plan, that particular experiment was repeated and not recorded. No sunlight came in, and the only light that was in the room was that of the lamps. After each experiment the boiling tube was emptied of water and sodium bicarbonate and refilled, making sure that every time the boiling tube contained the same quantities. I also left the fresh water a couple of minutes before adding the sodium bicarbonate, so the pondweed could get used to the water around it. ...read more.

Conclusion

This may have meant that the number of bubbles I counted was inaccurate. The only anomalous results we received were at the very beginning of the investigation. At first no bubbles were produced, so we changed for a different piece of pondweed. Fortunately the 2nd piece of pondweed worked well. The anomalous results were not included in the results table. If I did the experiment again to get better results, I would find a wider range of results and repeat each experiment three times. I would also move the pondweed by 2.5cm rather than 5cm. I couldn't do this originally because there wasn't enough time. My results allow me to reach a conclusion. If I were asked to make a prediction of how many bubbles would be released with a distance between the light source and weed of 12.5cm I could use my trend line and make an accurate prediction. To get more evidence to support my theory I would change the variable. I would perhaps alter the amount of sodium bicarbonate, but keep the light intensity constant. This would give me a broader idea on what factors affect the rate of photosynthesis. If I did extend the enquiry I think I would find that the rate of photosynthesis could be changed by a number of factors, each partly in control of the overall process. Ben Sims 10H Biology Coursework ...read more.

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